Method and apparatus for drilling multiple holes

ABSTRACT

A drilling unit and method of drilling a large number of holes of various sizes in a preset pattern in a single movement of the drilling head. A plurality of drills, each having a crank portion, are driven simultaneously by a common eccentric mechanism. The drills can be very closely spaced and are individually removable and replaceable without disturbing the overall arrangement.

United States Patent [151 3,637,317

Pomeroy et al. I 51 Jan. 25, 1972 54] METHOD AND APPARATUS FOR FOREIGNPATENTS 0R APPLICATIONS DRILLING MULTIPLE HOLES 917,525 9 1954 Germany..77 22 [72] Inventors: Paul E Pomeroy, 5424 Diane Ave San 631,49511/1949 Great Britain ..77/22 Diego, Calif. 921 17; Lucia B. Dixon, 8515P E F s H Sandstone Drive, Santee, Calif. 92071 "mary xammer. ranclsusar Attorney-Carl R. Brown [22] Filed: Sept. 2, 1969 21 Appl.No.:854,508 I [57] ABSTRACT A drilling unit and method of drilling a largenumber of holes of various sizes in a preset pattern in a singlemovement of the 2g drilling head. A plurality of drills, each having acrank portion, Id Se h L} 1 1 145 6 5. are driven simultaneously by acommon eccentric mechanism. 1 le 0 are 408/1 The drills can be veryclosely spaced and are individually removable and replaceable withoutdisturbing the overall ar- [56] References Cited rangemem' UNITED STATESPATENTS V is V, tl tq su- 'W'EE F 2,253,153 8/1941 Trumble et a1...-.....77/22 2,342,251 2/1944 Burt ..77/22 X 24 3o 1 4o 52 3o 4 4 201 58 6 58 5 2o 90 e 7e 78 i so 86 4 8 6 Xv I W x I00 00 VARIABLE SPEEDCONTROL SHEEHUF W PATENTED JANZS i972 ATTORNEY Fig.2

Fig.4

INVENTORS PAUL E. POMEROY LUCIA B. DIXON ATTORNEY PATENTEU JANZSIQTZ3,637,317 SHEET 3 OF 4 vsjfi 80 EU 82 7 L INVENTORS 78 I PAUL E. POMEROYJ BY LUCIA B. DIXON (40 gnaw ATTORNEY PATENTEUJANZSISYZ 3.637317 sum NF4 Fig. 9 l2 INVENTORS PAUL E. POMEROY LUCIA B. DIXON ATTORNEY BACKGROUNDOF THE INVENTION The present drilling machines consist of single ormultiple spindles with a chucking device on the end of each spindlecapable of rotating only one drill per spindle. The multiplespindledrilling machines have a small number of drills in a spaced arrangementlimited by the size of chucks or drill-holding means and the drivemechanism. The usual technique in using such drilling machines is todrill a similar hole in each of several workpieces, and then move allthe drill units to the next drilling position, by using a pantographtype, numerically controlled indexing machine. This is a time-consumingoperation especially for drilling an item such as a printed circuitboard with a large number of holes of varied sizes. The precise,repetitive position of the drilled holes as required in printed circuitboards is difficult to accomplish when the drills must be rechucked ateach change of hole size. Multiple-spindle drills which will drillseveral holes of different sizes in a single part have complex drivemechanisms and the proximity and pattern of the drilled holes is limitedby the chuck diameter and gear center distances in the drive mechanism.Each change of drill size requires rechucking of the drills which resultin small, undeterminable and highly undesirable deviations from optimumhole spacing.

SUMMARY OF THE INVENTION The drilling unit described herein can be setup with a large number of drills in any desired pattern and very closedrill spacing where necessary. Various sizes of drills can be includedin any location to provide for complete drilling of a workpiece in asingle operation or a single movement of the drill head. Each drill isdetachably connected to a crank element and all of the crank elementsare rotated simultaneously by a common eccentric mechanism, with thedrills held in precise alignment at all times. In a special drillingfixture the drill assembly is lowered on workpieces held in position andthe different sizes of drills are stepped in vertical relation topenetrate the workpiece in succession. Thus, if the drill sizes differsufficiently to require a speed change, this can be made as one size ofdrill completes penetration and the next size starts. The operationlends itself well to automated techniques, control being primarily thetimed, or drill position referenced, changes in drive speed. Individualdrills are readily removed or replaced without disturbing the rest ofthe assembly and, for some types of standardized patterns or parts ofthese patterns, groups of drills can be removed or inserted to obtainthe required arrangement.

While the drilling unit and method of this invention may be used todrill a plurality of small precision holes in close proximity throughaluminum or other materials capable of being drilled in one setup or onedrilling pass, it has particular application in the drilling of multipleholes in printed circuit boards.

Other objects and many advantages of this invention will become moreapparent upon a reading of the following detailed description and anexamination of the drawings, wherein like reference numerals designatelike parts throughout and in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevation view of acomplete multiple-drill unit;

FIG. 2 is a top plan view of the unit with part of the top cover cutaway;

FIG. 3 is a sectional view taken along line 3-3 of FIG. 2;

FIG. 4 is a sectional view taken along line 4-4 of FIG. 1;

FIG. 5 is a view showing the basic eccentric drive action;

FIG. 6 is a sectional view similar to a portion of FIG. 3, showing thestepped action of different drill sizes;

FIG. 7 is an enlarged detail of a single drill and driving crank;

FIG. 8 is a top plan view of a drill unit with an alternative drivemechanism, the top cover being cut away; and

FIG. 9 is a sectional view taken on line 99 of FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the form shown in FIGS. 1through 4, the structure-includes a drill head I0 which carries thedrills and actuating mechanism, and a base or bedplate I2 on which theworkpiece 14 is mounted. Head 10 comprises a thick platelike frame 16with a top cover 18 and lower frame elements 20 fixed thereon in anintegral assembly. Substantially at the center of head 10 is a verticaldrive shaft 22 joumaled in bearings 24 in the frame 16 and cover 18,said drive shaft carrying a drive gear 26. On opposite sides of thedrive shaft and parallel thereto are two driven shafts 28 joumaled inbearings 30 in the frame end cover, each driven shaft carrying a drivengear 32 meshing with drive gear 26. The gear mechanism is containedwithin top cover 18 and can be arranged as necessary with a suitablegear ratio to drive both driven shafts 28 in the same direction at thesame speed. Drive shaft 22 is coupled to a chuck 34, or

similar attachment, of a motor 36, which is provided with suitable speedcontrol means 38 of conventional type. Any convenient supporting meansmay be used to hold the motor and drill head. For example, the unitcould be mounted on and powered by a drill press, which would providethe necessary vertical motion of the head.

At the lower end of each driven shaft 28 is an eccentric boss 40 whichis secured in the center of a bearing 42, and fixed on the outside ofthe bearing is a horizontally extending attachment plate 44. Secured toand between the attachment plates 44 is a flat drive plate 46, which isgiven an orbital-type I motion when the eccentrics rotate. Each drivenshaft 28 has an extended pin portion 48 at the lower end, on which issecured a counterweight 50 to balance the eccentric mass and minimizevibration in operation.

On the underside of frame 16 is an upper bearing plate 52, above whichis a hardened thrust plate 54. These plates are shown recessed in theframe but could be externally mounted. Lower frame elements 20 haveinwardly projecting opposed flanges 56, between which is secured a lowerbearing plate 58. The drive plate 46 is between and in spaced parallelrelation to the upper and lower bearing plates 52 and 58 and all threeplates are identically drilled with the pattern and hole sizes to bedrilled in the workpiece. In FIG. 4 a few holes 60 and 62 of two sizesare shown as an example. Any num er of holes in any arrangement andcombination of hole sizes can be used to suit a specific workpiece.

Each drill is driven by a crank element 64, shown in detail in FIG. 7.The upper end 66 of the crank element is held in one hole in the upperbearing plate 52 and the lower end 68 projects downwardly through thelower bearing plate 58, the offset central portion 70 being held in thecorresponding hole in drive plate 46. A retaining collar 72 is fixed onlower end 68 above the lower bearing plate to hold the crank element inplace with the top against thrust plate 54. The axial displacementorthrow of offset portion 70 is equal to the throw of eccentric bosses 40,so that the eccentric orbital action of drive plate 46 causes all thecrank elements 64 to rotate equally. The action is shown in twopositions in FIG. 5 in a simplified form of structure in which the driveplate 46A is shown as driven directly by an eccentric 40A, for clarityof illustration. The tip of each lower end 68 has a driving dog 74formed therein to interfit with a corresponding dog 76 on the upper endof a drill bit 78. Other types of connections may be used, but theconfiguration shown is a simple and convenient connection which does notincrease the overall diameter of the junction. Each drill bit 78 has aretaining collar 80 fixed just below the dog 76 and all the drill bitsare held in driving connection by a retaining plate 82 drilled with thecorresponding hole pattern. The retaining plate 82 is secured to theunderside of lower frame elements 20, parallel to lower bearing plate58. All assembly is made by capscrews or similar means as used in jigand tool construction.

Below the head is a pressure plate 84 which is vertically slidablymounted on posts 86 secured in lower frame elements 20. The lower endsof posts 86 have enlarged heads 88 and the pressure plate is biaseddownwardly against the heads by load springs 90 concentric with theposts. Pressure plate 84 is also drilled with the complete hole patternand stabilizes the ends of the drill bits 78.

Bedplate 12 has fixed vertical guide pins 92 at suitable positions toslide in close fitting guide bores 94 in the head 10, and maintain thehead in precise alignment over the bedplate. workpiece 14 is held inplace on locating pins 96 projecting upwardly from bedplate 12. Otherlocating or stop means may be used for workpieces which cannotconveniently be provided with tooling holes to lit the pins. Pressureplate 84 has clearance holes 98 for the locating pins 96 and bedplate 12has clearance holes 100 for posts 86, when the head is lowered fordrilling. Bedplate 12 has a cavity 102 below the workpiece for drillclearance, or could be provided with suitable backing material if theworkpiece needs support.

In FIG. 3, it will be seen that the smaller drill bits extend almostthrough pressure plate 84, while the larger drill bits are somewhatshorter. When drilling, the smaller drill bits'will be completelythrough the workpiece 142.5 the larger drill bits come into contact withthe workpiece, as in FIG. 6. This affords an opportunity to changedrilling speed to suit the next size of drill bit. With severaldifferent sizes of drills, each size would be axially staggered orstepped in this manner if the size change was sufficient to warrant achange in speed, which could be controlled by timing means or drillposition sensing means. By such a technique all holes are drilled in oneoperation of the unit and the sequence of actions is readily adaptableto automatic control. With suitable indexing or positioning means,workpieces could be fed through the unit in interconnected or strip formto speed up production.

An alternative form of the eccentric drive mechanism is shown in FIGS. 8and 9 in which a single eccentric boss 104 is carried directly on adrive shaft 106 journaled in bearings 108 in a head frame 110. Below theframe are lower frame elements 112 and 114, which support a lowerbearing plate 58 and retaining plate 82, the upper bearing plate 52 andthrust plate 54 being secured to the underside of the frame in themanner and relationship described above for the head 10. Crank elements64 and drill bits 78 are also mounted in the same manner and the actionis similar to that described. However, the drive plate 116 is secured toa single attachment plate 118 mounted on a bearing 120 around theeccentric boss 104. A counterweight 122 is fixed on the lower end ofdrive shaft 106 for balancing. The other end of drive plate 116 isattached to and supported by a parallel motion linkage 124 comprising apair of links 126 pivotally attached to the drive plate, a pair ofsimilar links 128 pivotally connected between links 126 and the lowerframe element 112, and a connecting bar 130 interconnecting thejunctions of links 126 and 128. The parallel linkage is merely onesuitable form and other such means may be used. As the drive plate makesits eccentric orbital motion, the linkage maintains the longitudinal andlateral alignment bearing plates.

The arrangement of the pressure plate, bedplate and workpiece mountingis also as described above and the elements are correspondingly numberedin FIG. 9. Except for the simplified drive means, the operation is thesame as that of the geared dual eccentric form of the unit.

The use of crank elements to drive the drills makes it possi ble to usevery close drill spacing. in fact the center to center spacing ofadjacent drills may be less than the combined diameters of the drills.Merely enough space to provide working clearance for the retainingcollars is all that is required. Normally a matched set of plates,comprising the upper and lower bearing plates 52 and 58, drive plate 46,retaining plate 82 and pressure plate 84 would be made up for each work-.piece. For some pieces having a regular hole pattern, or utilizing partof the hole pattern of another, the appropriate drill bits can beinserted in the required pattern. Only the retaining plate 82 need beremoved for this operation if the appropriate crank elements are inplace, since the crank elements can remain whether or not they areconnected to drill bits. Since all holes are drilled in one operationwith precisely positioned drills, accuracy is consistent through a largenumber of drilled parts.

Having described our invention, we now claim:

1. A multiple-hole drilling unit, comprising,

a head having a plurality of drill bits rotatably mounted therein inspaced parallel relation in a present pattern, each of said drill bitshaving a crank element connected thereto in a driving relation,

a drive element interconnecting all of said crank elements in commonalignment,

driven eccentric actuating means coupled to said drive element formoving the drive element with an orbital action corresponding to thethrow of said crank elements,

and said drill bits are detachable from said crank elements and havemeans for retaining said drill bits in said head independently of thecrank elements.

2. A multiple-hole drilling unit, comprising,

a head having a plurality of drill bits rotatably mounted therein inspaced parallel relation in a preset pattern, each of said drill bitshaving a crank element connected thereto in driving relation, A

a drive element interconnecting all of said crank elements in commonalignment,

driven eccentric actuating means coupled to said drive element formoving the drive element with an orbital action corresponding to thethrow of said crank elements,

said head has an upper bearing plate and a lower bearing plate securedthereto in spaced parallel relation,

said crank elements have end portions journaled in said bearing plates,

and said drive elementbeing mounted between the bearing plates.

3. A drilling unit according to claim 2, wherein,

said drive element comprises a drive plate through which said crankelements extend in close-fitting rotational engagement.

4. A drilling unit according to claim 3 and including,

at least one attachment plate to which said drive plate is detachablysecured,

said eccentric actuating means including an eccentric boss rotatablymounted in said attachment plate.

5. A drilling unit according to claim 2 wherein,

said crank elements have retaining collars fixed thereon above saidlower bearing plate and drill bit driving connections extending belowsaid lower bearing plate.

6. A drilling unit according to claim 5 wherein,

said drill bits have end portions interfitting with said drivingconnections, and retaining collars fixed thereon below said endportions,

said head having a drill bit retaining plate removably secured theretoand through which said drill bits extend with their retaining collarsabove the retaining plate.

7. A drilling unit according to claim 6 and including,

pressure plate means vertically, slidably mounted below said head,

and means for biasing said pressure plate means downwardly from saidhead, said drill bits extending through and being stabilized by saidpressure plate means.

8. A drilling unit according to claim 7 and including,

a bedplate having workpiece-aligning means thereon,

said bedplate having guide means engaging said head to guide the headrelative to a workpiece,

and said pressure plate means for holding the workpiece in place belowthe drill bits and during this drilling operatron.

'9. A drilling unit according to claim 1 wherein,

said actuating means comprises a pair of synchronously driven eccentricelements connected to and supporting said drive element.

10. Adrilling unit according to claim 1 wherein,

said actuating means comprises an eccentric element connected to oneside of said drive element,

and parallel motion linkage connected to and supporting the other sideof the drive element.

11. A multiple-hole drilling unit, comprising,

a head having a plurality of drill bits rotatably mounted therein inspaced parallel relation in a preset pattern, each of said drill bitshaving a crank element connected thereto in driving relation,

a drive element interconnecting all of said crank elements in commonalignment,

driven eccentric actuating means coupled to said drive element formoving the drive element with an orbital action corresponding to thethrow of said crank elements,

and said actuating means comprises a pair of synchronously driveneccentric elements connected to and supporting said drive element.

12. A multiple-hole drilling unit, comprising,

a head having a plurality of drill bits rotatably mounted therein inspaced parallel relation in a preset pattern, each of said drill bitshaving a crank element connected thereto in driving relation,

a drive element interconnecting all of said crank elements in commonalignment,

driven eccentric actuating means coupled to said drive element formoving the drive element with an orbital action corresponding to thethrow of said crank elements,

said actuating means comprises an eccentric element connected to oneside of said drive element,

and parallel motion Iinkage connected to and supporting the other sideof the drive element.

13. The method of drilling multiple holes in a workpiece comprising thesteps of,

positioning a plurality of drills to drill a given multiple-hole patternin a workpiece,

rotating said plurality of drills by a single drive mechanism,

aligning a workpiece to the cutting ends of said drills,

moving the cutting ends of said plurality of rotating drills en massewith one downward movement to contact said workpiece and drill holestherein,

positioning the cutting ends of groups of different size drills atdifferent distances from the workpiece,

and selectively setting the speed of rotation of each of said groups tocorrespond to the optimum cutting speed for the group upon the cuttingends of each of said groups reaching the position for contacting thework.

1. A multiple-hole drilling unit, comprising, a head having a pluralityof drill bits rotatably mounted therein in spaced parallel relation in apreset pattern, each of said drill bits having a crank element connectedthereto in a driving relation, a drive element interconnecting all ofsaid crank elements in common alignment, driven eccentric actuatingmeans coupled to said drive element for moving the drive element with anorbital action corresponding to the throw of said crank elements, andsaid drill bits are detachable from said crank elements and have meansfor retaining said drill bits in said head independently of the crankelements.
 2. A multiple-hole drilling unit, comprising, a head having aplurality of drill bits rotatably mounted therein in spaced parallelrelation in a preset pattern, each of said drill bits having a crankelement connected thereto in driving relation, a drive elementinterconnecting all of said crank elements in common alignment, driveneccentric actuating means coupled to said drive element for moving thedrive element with an orbital action corresponding to the throw of saidcrank elements, said head has an upper bearing plate and a lower bearingplate secured thereto in spaced parallel relation, said crank elementshave end portions journaled in said bearing plates, and said driveelement being mounted between the bearing plates.
 3. A drilling unitaccording to claim 2, wherein, said drive element comprises a driveplate through which said crank elements extend in close-fittingrotational engagement.
 4. A drilling unit according to claim 3 andincluding, at least one attachment plate to which said drive plate isdetachably secured, said eccentric actuating means including aneccentric boss rotatably mounted in said attachment plate.
 5. A drillingunit according to claim 2 wherein, said crank elements have retainingcollars fixed thereon above said lower bearing plate and drill bitdriving connections extending below said lower bearing plate.
 6. Adrilling unit according to claim 5 wherein, said drill bits have endportions interfitting with said driving connections, and retaininGcollars fixed thereon below said end portions, said head having a drillbit retaining plate removably secured thereto and through which saiddrill bits extend with their retaining collars above the retainingplate.
 7. A drilling unit according to claim 6 and including, pressureplate means vertically, slidably mounted below said head, and means forbiasing said pressure plate means downwardly from said head, said drillbits extending through and being stabilized by said pressure platemeans.
 8. A drilling unit according to claim 7 and including, a bedplatehaving workpiece-aligning means thereon, said bedplate having guidemeans engaging said head to guide the head relative to a workpiece, andsaid pressure plate means for holding the workpiece in place below thedrill bits and during this drilling operation.
 9. A drilling unitaccording to claim 1 wherein, said actuating means comprises a pair ofsynchronously driven eccentric elements connected to and supporting saiddrive element.
 10. A drilling unit according to claim 1 wherein, saidactuating means comprises an eccentric element connected to one side ofsaid drive element, and parallel motion linkage connected to andsupporting the other side of the drive element.
 11. A multiple-holedrilling unit, comprising, a head having a plurality of drill bitsrotatably mounted therein in spaced parallel relation in a presetpattern, each of said drill bits having a crank element connectedthereto in driving relation, a drive element interconnecting all of saidcrank elements in common alignment, driven eccentric actuating meanscoupled to said drive element for moving the drive element with anorbital action corresponding to the throw of said crank elements, andsaid actuating means comprises a pair of synchronously driven eccentricelements connected to and supporting said drive element.
 12. Amultiple-hole drilling unit, comprising, a head having a plurality ofdrill bits rotatably mounted therein in spaced parallel relation in apreset pattern, each of said drill bits having a crank element connectedthereto in driving relation, a drive element interconnecting all of saidcrank elements in common alignment, driven eccentric actuating meanscoupled to said drive element for moving the drive element with anorbital action corresponding to the throw of said crank elements, saidactuating means comprises an eccentric element connected to one side ofsaid drive element, and parallel motion linkage connected to andsupporting the other side of the drive element.
 13. The method ofdrilling multiple holes in a workpiece comprising the steps of,positioning a plurality of drills to drill a given multiple-hole patternin a workpiece, rotating said plurality of drills by a single drivemechanism, aligning a workpiece to the cutting ends of said drills,moving the cutting ends of said plurality of rotating drills en massewith one downward movement to contact said workpiece and drill holestherein, positioning the cutting ends of groups of different size drillsat different distances from the workpiece, and selectively setting thespeed of rotation of each of said groups to correspond to the optimumcutting speed for the group upon the cutting ends of each of said groupsreaching the position for contacting the work.